Storing device for fuel assemblies

ABSTRACT

A storing device for fuel assemblies includes a supporting grid with a substantially square lattice and a plurality of tubes of substantially square cross-section each adapted to contain one fuel assembly. There are retaining devices for holding tubes in position with respect to the grid. The walls of the tubes are coated with absorbing material. Each of the retaining devices is arranged to hold a pair of mutually parallel walls of different tubes having a gap between them, with the walls crossing a side of the lattice. The gap contains a layer of absorbing material, and is sealed water-tightly at the top and bottom portions of the gap.

'1 Umtd States atent 11 3,859,533 Suvanto Jan. 7, 1975 [54] STORINGDEVICE FOR FUEL ASSEMBLIES 3,229,096 1/1966 Bonilla et al 250/507 I t At y d [75] nven or ntti Suvanto, Vas eras Swe en Primary Examiner HamldA. Dixon [73] Assignee: AB Asea-Atom, Vasteras, Sweden [22] Filed: Nov.15, 1973 ABSTRACT [211 App] No 416 182 A storing device for fuelassemblies'includes a supporting grid with a substantially squarelattice and a plurality of tubes of substantially square cross-sectionForeign Application i y Data each adapted to contain one fuel assembly.There are Dec, 21, 1972 Sweden 16779/72 retaining devices for holdingtubes in position with respect to the grid. The walls of the tubes arecoated [52] US. Cl. 250/507, 250/518 h ing m eri l. Each of theretaining devices [51] Int. Cl. G21f 5/00 i nged to hold a pair ofmutually parallel walls of [58] Field of Search 250/506, 507,515, 518different tubes h ing a gap w n h m, wi h h walls crossing a side of thelattice, The gap contains a [56] References Cited layer of absorbingmaterial, and is sealed water-tightly UNITED STATES PATENTS at the topand bottom portions of the gap. 3,119,933 1/1964 Allen 250/507 1 Claim,2 Drawing Figures Patented Jan. 7, 1975 3,859,533

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BACKGROUND OF THE INVENTION 1. Field of the Invention The present patentapplication relates to a storing device for fuel assemblies.

2. The Prior Art Storing devices for fuel assemblies are usuallyconstructed with assembly positions so thinly distributed that there isno risk of criticality. This, however, requires a relatively largedistance between the assemblies and, as the required number of storingpositions is great, about 1,000 to a medium-sized reactor station, thespace which is needed for fuel storage will be considerable.

The assemblies can be placed close to each other if a sufficient amountof absorbing material of penetrating radiation is placed between theassemblies. Most of the absorbing materials must be encapsuled in ordernot to be dissolved or corroded by the water. The materials which can beused uncapsuled, for example hafnium, are very expensive.

SUMMARY OF THE INVENTION In the device according to the invention, thestoring tubes are assembled in such a way that a space which isnecessary for absorbing materials is formed between the tubes when theyare put together into a unit. The construction consists of square tubeswhich are provided with absorbing material all around them. Applicationof the absorbing layer can be performed by metal spraying, byelectrolysis or in the form of thin sheet or foil. The gaps betweenadjacent tubes are sealed by welding at top and bottom. The sides of theconstruction which do not face other tubes are provided with coverplates welded to the upper and lower edges of the tubes. The units canbe so small as 4 to 8 positions but can also comprise all 1,000positions. Units which are very large, however, are impractical from thepoint of view of handling and prefabrication.

Furthermore, according to the invention, a grid is provided which isformed of upstanding wall portions crossing each other, with notchesbetween the tubereceiving portions, in which the walls of adjacent tubesengage with a space between them which is filled with absorbing medium.The spaces are sealed at top and bottom by valves or the like.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described withreference to the accompanying drawing in which FIG. 1 shows a deviceaccording to the invention in horizontal section along the line I I ofFIG. 2, and FIG. 2 shows a vertical section of the same device along theline IIII of FIG. 1, FIG. 1 showing the storing device without fuelassemblies and FIG. 2 with fuel assemblies.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, 1 designates asupporting grid which is constituted by a plurality of sheet elements 2resting on their ends and crossing each other and welded together. Thesupporting grid 1 is supported by a plurality of supporting studs 3which are arranged on the floor of the fuel basin. A number of storingtubes 4 are positioned on the supporting grid 1, which is provided withretaining means of such a nature that accurate positions are ensured forthe tubes. The retaining means in a simple form consist of notches 5 inthe sheet element 2. In each notch 5 the width is such that two paralleltubular walls 6 and 7, belonging to two different storing tubes with anintermediary gap 8 for absorbing material, can be inserted into thenotch 5. The gaps 8 are sealed at the upper and lower edges by thewelding seams 9 and 10, which, together with a cover plate surroundingthe whole storing device, ensures a watertight enclosure of theabsorbing material arranged between the storing tubes.

The sheet elements 2 are made with oblique control edges 11, whichresults in a centering of each fuel assembly 12 with respect to thecorresponding storing tubes.

I claim:

1. Storing device for fuel assemblies of substantially squarecross-section, comprising a supporting grid (1) with a substantiallysquare lattice, a plurality of tubes (4), the tubes having substantiallysquare cross section and being adapted to contain one fuel assemblyeach, a plurality of retaining means (5) for holding said tubes inposition with respect to said supporting grid, an absorbing material (8)coating the walls of said tubes, each of said retaining means (5) beingadapted to hold a pair (6, 7) of mutually parallel walls belonging todif ferent tubes and arranged with a gap (8) between them, said wallscrossing a side of said lattice, said gap containing a layer ofabsorbing material, the gap between said walls being sealedwater-tightly at the top and bottom portions of said gap.

1. Storing device for fuel assemblies of substantially squarecross-section, comprising a supporting grid (1) with a substantiallysquare lattice, a plurality of tubes (4), the tubes having substantiallysquare cross-section and being adapted to contain one fuel assemblyeach, a plurality of retaining means (5) for holding said tubes inposition with respect to said supporting grid, an absorbing material (8)coating the walls of said tubes, each of said retaining means (5) beingadapted to hold a pair (6, 7) of mutually parallel walls belonging todifferent tubes and arranged with a gap (8) between them, said wallscrossing a side of said lattice, said gap containing a layer ofabsorbing material, the gap between said walls being sealedwater-tightly at the top and bottom portions of said gap.